The present invention relates to machines for cutting earth formations and, more particularly, to the mounting of an annular cutter chain on a rotary sprocket wheel assembly.
Machines for cutting earth formations such as coal and other mineral deposits, rocky soil, etc., often employ bits which are mounted on endless chains, the latter being driven to scrape the cutter bits against the formation being cut, as disclosed for example in a mining machine described in U.S. Pat. No. 3,305,273 issued to Kilbourne on Feb. 21, 1967.
The cutter chain may comprise one or more annular rows of links mounted on a rotary sprocket wheel assembly. The links are connected together by pins which extend parallel to the axis of rotation. The pins are engaged by teeth on the sprocket wheel to effect rotation of the chain. The links carry sockets for the reception of the cutter bits. A chain of this fashion is disclosed, for example in U.S. Pat. No. 3,784,259 issued to Munger et al on Jan. 8, 1974.
In many instances the cutter chains are mounted in elliptical fashion on a pair of spaced sprocket wheel assemblies, one of which is driven. Usually the chain is installed while in non-endless condition, i.e., with one chain pin removed. One or more of the sprocket wheel assemblies can be mounted for adjustable positioning to reduce the center-to-center spacing between the sprocket wheel assemblies. Thus, the final pin can be installed relatively easily with the chain in a slackened condition. Thereafter, the adjustable sprocket wheel assembly is adjusted to tighten the chain. By thus tightening the chain, a quieter and less wear producing operation of the chain is provided.
In other instances, certain design ad space requirements dictate that the cutter chains be wrapped in circular fashion around a single sprocket wheel assembly. This arrangement may be found in some mining machines which include a vehicle body which carries a rotary cutter mounted for rotation on a horizontal transverse shaft. The cutter includes auger drums mounted at and near the ends of the shaft, with the cutter chains located between the drums and mounted in circular fashion around a single sprocket wheel assembly keyed to the shaft. The sprocket wheel assembly may comprise a plurality of longitudinally spaced sprocket wheels which support opposite ends of the chain pins.
Whereas cutter chains mounted on a pair of sprocket wheel assemblies can be conveniently mounted in slackened condition by converging the sprocket centers, such an expedient is not available when mounting the chain in circular endless fashion around one sprocket wheel assembly. In the latter case, the chain can be deliberately sized of sufficient length so as to be in slackened condition when wrapped around the sprocket wheel. This facilitates insertion of the final chain pin, but the ensuing operation of the relatively loose chain produces excessive levels of noise and wear. On the other hand, if the chain is too tight, installation of the final chain pin is very difficult.
It is, therefore an object of the present invention to minimize or obviate problems of the type discussed above.
It is another object of the invention to provide a novel sprocket wheel for a cutting chain.
It is an additional object of the invention to enable a cutter chain to be conveniently installed in circular fashion around a sprocket wheel without the subsequent production of excessive noise and wear during operation.
It is yet another object of the invention to provide a sprocket wheel for a cutting chain which automatically compensates for wear.